A cellular communications network typically includes a variety of communication nodes coupled by wireless or wired connections and accessed through different types of communications channels. Each of the communication nodes includes a protocol stack that processes the data transmitted and received over the communications channels. Depending on the type of communications system, the operation and configuration of the various communication nodes can differ and are often referred to by different names. Such communications systems include, for example, a Code Division Multiple Access 2000 (CDMA2000) system and a Universal Mobile Telecommunications System (UMTS).
Third generation wireless communication protocol standards (e.g., 3GPP-UMTS, 3GPP2-CDMA2000, etc.) may employ a dedicated traffic channel in the uplink (e.g., a communication flow between a mobile station (MS) or User Equipment (UE), hereinafter referred to as a user, and a base station (BS) or Node B. The dedicated physical channel may include a data part (e.g., a dedicated physical data channel (DPDCH) in accordance with UMTS Release 4/5 protocols, a fundamental channel or supplemental channel in accordance with CDMA2000 protocols, etc.) and a control part (e.g., a dedicated physical control channel (DPCCH) in accordance with UMTS Release 4/5 protocols, a pilot/power control sub-channel in accordance with CDMA2000 protocols, etc.).
Newer versions of these standards, for example, Release 6 of UMTS provide for high data rate uplink channels referred to as enhanced dedicated physical channels. These enhanced dedicated physical channels (E-DCHs) may include an enhanced data part (e.g., an enhanced dedicated physical data channel (E-DPDCH) in accordance with UMTS protocols) and an enhanced control part (e.g., an enhanced dedicated physical control channel (E-DPCCH)) in accordance with UMTS protocols.
FIG. 1 illustrates a conventional wireless communication system 100 operating in accordance with UMTS protocols. Referring to FIG. 1, the wireless communication system 100 may include a number of Node Bs such as Node Bs 120, 122 and 124, each serving the communication needs of a first type of user 110 and a second type of user 105 in their respective coverage area. The first type of user 110 may be a higher data rate user such as a UMTS Release 6 user, referred to hereinafter as an enhanced user. The second type of user may be a lower data rate user such as a UMTS Release 4/5 user, referred to hereinafter as a legacy user. The Node Bs are connected to an RNC such as RNCs 130 and 132, and the RNCs are connected to a MSC/SGSN 140. The RNC handles certain call and data handling functions, such as, autonomously managing handovers without involving MSCs and SGSNS. The MSC/SGSN 140 handles routing calls and/or data to other elements (e.g., RNCs 130/132 and Node Bs 120/122/124) in the network or to an external network. Further illustrated in FIG. 1 are interfaces Uu, Iub, Iur and Iub between these elements.
FIG. 2A illustrates an example frame structure for the UMTS uplink dedicated physical channels (DCHs). As shown, each frame 200 may have a length of, for example, 10 milliseconds (ms) and may be partitioned into 15 slots 205. Each slot 205 may have a length of, for example, 2560 chips, which corresponds to one power-control period, and may have a duration of, for example, ⅔ ms.
The uplink dedicated physical channels include a DPDCH 240 and a DPCCH 220, and each of the DPCCH 220 and the DPDCH 240 may be code multiplexed. The DPDCH 240 may include information transmitted from the legacy user 105. The DPCCH 220 may include control information, for example, a pilot signal 221, transmit power control information (e.g., transmit power control (TPC) bits) 222, a transport format combination indicator (TFCI) value 223 and feedback information (FBI) 224 (which may be used or unused).
The TFCI 223 may inform the Node B 120/122/124 of the transport format information (e.g., voice and/or data packets sizes, coding types, etc.) transmitted from the legacy user 105. The legacy user 105 and the Node Bs 120/122/124 may generate transmit power control (TPC) commands 222 to control each others transmit power. When user 105 communicates with, for example, a single Node B 120/122/124, a single transmit power control command may be received in the TPC information 222 of each timeslot.
While FIG. 2A illustrates a 3GPP-UMTS uplink frame structure, a 3GPP2-CDMA2000 uplink frame structure may be similar. However, a typical 3GPP2-CDMA2000 uplink frame structure does not include the above-described TFCI 223 and FBI 224.
FIG. 2B illustrates an example frame structure for the enhanced dedicated channels (e.g., E-DPCCH and E-DPDCH) in the uplink direction. As shown, each frame 200a may have a length of, for example, 10 milliseconds (ms) and may be partitioned into 5 sub-frames each including 3 slots. Each slot 205a may have a length of, for example, 2560 chips, and may have a duration of, for example, ⅔ ms. Consequently, each sub-frame may have a duration of 2 ms.
As discussed above, an E-DCH includes an E-DPDCH 240a and an E-DPCCH 220a, and each of the E-DPCCH 220a and the E-DPDCH 240a may be code multiplexed. The E-DPCCH 220a carries control information for an associated E-DPDCH 240a. This control information includes three components: a re-transmission sequence number (RSN), a transport format indicator (TFI) and a happy bit. The RSN indicates the transmission index of an associated packet transmitted on the E-DPDCH, has a maximum value of 3 and is represented by two bits. The TFI indicates the data format for the transport channel carried by the associated E-DPDCH (e.g., transport block size, transmission time interval (TTI), etc.) and is represented by 7 bits. The happy bit is a binary indicator, which may be used by a UE to inform one or more NodeBs whether the UE is satisfied with the current setup of the E-DCH channels and is represented by a single bit. For example, UE 110 of FIG. 1 may use this indicator to inform one of the NodeBs 120/122/124 that the UE 110 may handle greater data capacity. In other words, the happy bit is a rate increase request bit.
E-DCHs are often used together with the high speed downlink packet access (HSDPA). As a result, the UE may also transmit the uplink HS-DPCCH, which carries the acknowledgment and channel quality indicator (CQI) for the downlink.
FIG. 2C illustrates a frame structure of an uplink HS-DPCCH. As shown, HS-DPCCH frames are transmitted in subframes, each of which spans three timeslots Ts. Each timeslot Ts may be 2560 chips in length. The first timeslot HARQ-ACK carries the acknowledge bit (ACK-NACK) and the final two timeslots CQI carry the CQI information. HS-DPCCH is code and I/Q multiplexed with the DPCCH and the DPDCH and transmitted to the Node B. When transmitted, the HS-DPCCH subframe is offset from the DPCCH frame in a unit of 256 chip symbols depending on the time relationship between the downlink DPCH and the HS-DSCH of the serving sector
FIG. 3 illustrates a conventional UMTS uplink transmitter 300 located at the enhanced UE 110 of FIG. 1 and a receiver 350 located at one of the NodeBs 120/122/124. The conventional transmitter 300 and receiver 350 of FIG. 3 may transmit and receive E-DCHs, DPCCHs and/or HS-DCHs.
Referring to FIG. 3, data associated with an upper layer enhanced dedicated transport channel (E-DCH) may be processed into E-DPDCH frames at the transmission channel processing block 302. The frames may be binary phase shift keying (BPSK) modulated and orthogonally spread at the modulation and orthogonal spreading unit 304. The spread modulated frames are received by the gain unit 306 where an amplitude of the spread, modulated frames may be adjusted. A combiner 333 receives the output of the gain unit 306.
Still referring to FIG. 3, the 2 RSN bits, the 7 TFI bits and the 1 happy bit are mapped into a 10-bit E-DPCCH word, which may be control information for an associated E-DPDCH frame having a transmission time interval (TFI) of, for example, 2 ms or 10 ms. The 10-bit E-DPCCH word may then be coded into a 30-bit coded sequence at an FEC unit 308. The 30-bit coded sequence is modulated at a BPSK Modulator 310 and orthogonally spread at an orthogonal spreading unit 312. The output from the orthogonal spreading unit 312 is gain adjusted at a gain unit 331 and output to the combiner 333.
Similar to the above E-DPCCH, well-known DPCCH frames used in determining channel estimates are modulated at a BPSK Modulator 314, and the modulated frames are orthogonally spread at an orthogonal spreading unit 316. The output from the orthogonal spreading unit 316 is gain adjusted at a gain unit 318 and output to the combiner 335.
Referring still to FIG. 3, data associated with an upper layer dedicated transport channel (DCH) may be processed into DPDCH frames at the transmission channel processing block 320. The frames may be binary phase shift keying (BPSK) modulated and orthogonally spread at the modulation and orthogonal spreading unit 322. The spread modulated frames are received by the gain unit 324 where an amplitude of the spread modulated frames may be adjusted. A combiner 337 receives the output of the gain unit 324.
Similar to the above E-DPCCH and DPCCH, well-known HS-DPCCH frames are modulated at a BPSK Modulator 326, and the modulated frames are orthogonally spread at an orthogonal spreading unit 328. The output from the orthogonal spreading unit 328 is gain adjusted at a gain unit 330 and output to the combiner 337.
The outputs of each of the gain units 324 and 330 are combined at combiner 337, and the resultant combined signal is output to combiner 335. The combiner 335 combines the output of the gain unit 318 with the output from the combiner 337, and outputs the resultant to the combiner 333. The outputs from gain units 306, 331 and the combiner 335 (e.g., code-division multiplexed) are combined into a combined signal by combiner unit 333. The combined signal is scrambled and filtered by a shaping filter 332, and the output of the shaping filter 332 is sent to the receiver 350 via a propagation channel 334 (e.g., over the air).
At the receiver 350, the transmitted signal is received over the propagation channel 334, and input to an E-DPDCH physical channel processing block 336, an E-DPCCH soft-symbol generation block 338 and a DPCCH channel estimation block 340. As is well-known in the art, the DPCCH channel estimation block 340 generates channel estimates using pilots transmitted on the DPCCH. The channel estimates may be generated in any well-known manner, and will not be discussed further herein for the sake of brevity. The channel estimates generated at the DPCCH channel estimation block 340 may be output to the E-DPDCH transport channel processing block 342 and to E-DPCCH processing block 338.
At the E-DPCCH processing block 338, the DPCCH channel estimates are used to generate E-DPCCH soft-symbols. The E-DPCCH soft-symbols are used in recovering the transmitted E-DPCCH word at the E-DPCCH processing block 338. The E-DPCCH processing block 338 also performs control channel DTX detection to determine that an E-DPCCH and E-DPDCH pair has been received at the receiver 350. The DPCCH channel estimates and the E-DPCCH word are sent to the E-DPDCH physical channel processing block 336 and the E-DPDCH transport channel processing block 342 for use in processing the E-DPDCH if an E-DPDCH is detected at the E-DPCCH processing block 338.
Still referring to FIG. 3, the E-DPDCH physical channel processing block 336 may generate a first received data frame from the received signal. In one example, the E-DPDCH physical channel processing block 336 may use maximal ratio combining techniques to generate the first received data frame, where the first received data frame includes a plurality of soft-symbols referred to as a soft-symbol sequence. The soft-symbol sequence may be an estimate of the symbol sequence included in the data frame transmitted by the transmitter 300. The soft-symbol sequence may be output to a transport channel processing block 342. The transport channel processing block 342 may perform HARQ combining, turbo decoding and CRC checks to recover the transmitted transport channel data bits.
Conventionally, each UE in a cell has a maximum transmit power with which the UE may transmit. When a UE is at a cell edge or in deep fade, the NodeB may request transmission power that exceeds a maximum transmit power limit. However, when the UE exceeds this transmission power limit, and the NodeB requests more transmit power, the transmission power (or gain) of the uplink E-DPCCH must be reduced first in order to bring the total transmit power within the UE's maximum transmit power limit without reducing the power of other legacy channels such as the DPCCH, DPDCH and/or the HS-DPCCH. If, as a result, the E-DPDCH power is below a certain level, the UE may mute the transmission of the E-DPDCH completely if a DPDCH is present.
Because the E-DPDCH transmission power reduction is transparent to higher layers, it is unknown to the NodeB. In some cases, the NodeB needs to know the proper scaling of a turbo decoder input soft symbol. In another example, the RNC should know the power reduction status of the E-DPDCH for driving outer loop power control. In this case, if power reduction on the E-DPDCH is detected, the signal-to-interference ratio (SIR) target may be adjusted differently.
For an uplink transmitter at the UE, when a maximum transmit power is exceeded, the UE must reduce the E-DPDCH gain factor to bring the total transmit power within the maximum transmit power limit. The power reduction is performed for each E-DPDCH timeslot (e.g., at the E-DPDCH timeslot boundary) because the amount of power reduction may vary from slot to slot depending on the loading of other code channels.